The objectives of this project are to determine how 2450 MHz microwave radiation interacts with biological material at the cellular and subcellular level, to observe any effects of this interaction, and to relate the amount of microwave energy absorbed to the effect. The biological specimens include macrophages, cardiac cells, lysosomes, and cellular enzymes. For these experiments, a waveguide exposure apparatus has been used which can maintain the specimens at physiologic temperatures (37 degrees C + 0.25 degrees C) at specific absorption rates up to 100 mW/g. No effects were noted on in vitro activity of (creatine phosphokinase and acetylcholinesterase) at SAR's up to 50 mW/g. Embryonic cardiac cells obtained from 9-day-old quail, exhibited an increase in cell membrane permeability to typan blue at SAR's of 10, 50 and 100 mW/g, following 90 minutes exposure. Cellular damage was noted at an SAR of 100 mW/g. Lysosome fragility was not influenced by microwaves at SAR's up to 100 mW/g and exposure durations of 90 min. Methods for examining the influence of microwave radiation on mitochondria and macrophages are being developed.